Composite separation membrane

Reference Example 1

[0047]The porous supporting membrane reinforced with a fiber, used in the present invention, was produced in accordance with the following approach.

[0048]Taffeta (150-denier multifilament yarn for both warp yarn and weft yarn, weaving density: 90 yarns/inch in the length direction and 67 yarns/inch, thickness: 160 μm) composed of a 30 cm long×20 cm wide polyester fiber was fixed to a glass plate, and a 15 weight % dimethylformamide solution of polysulfone (Udel (Registered Trademark) produced by Amoco, P-3500) was casted thereon at room temperature (25° C.) to provide a thickness of 200 μm, immediately followed by immersion in pure water and leaving as it was for 5 minutes, thereby obtaining a porous supporting membrane. The pure water permeation coefficient of the thus obtained porous supporting membrane was 0.005 to 0.01 kg/cm2/sec/atm (about 0.001 to 0.002 g/cm2/sec/MPa), which was measured at a pressure of 0.1 MPa and a temperature of 25° C. In addition, the average pore size at the surface of the obtained porous supporting membrane was 20 to 50 nm, and the thickness of the polysulfone moiety thereof was 50 μm.

Example 1

[0049]The porous supporting membrane produced in accordance with Reference Example 1 was brought into contact with an isopropyl alcohol solution containing 3.6 weight % of sodium styrenesulfonate, 0.4 weight % of Methacryl-POSS (polyhedral oligomeric silsesquioxane), 0.24 weight % of 2,2-dimethoxy-2-phenylacetophenone as an α-hydroxyacetophenone type photopolymerization initiator, and 33.5 weight % of pure water for 1 minute, and nitrogen was sprayed from an air nozzle to remove the extra solution from the surface of the porous supporting membrane, thereby forming a layer of the solution on the porous supporting membrane. Then, with the use of an excimer lamp (UER 20-172) produced by Ushio, inc., capable of irradiation with ultraviolet rays of 172 nm, the distance between the excimer lamp and the porous supporting membrane was set to 1 cm under a nitrogen atmosphere with an oxygen concentration of 0.1% or less, and irradiation with ultraviolet rays was carried out for 5 minutes to produce a composite separation membrane with a polymer of a polyhedral silsesquioxane and a hydrophilic monomer formed on the surface of the porous supporting membrane. Then, immersion in a 10 weight % isopropyl alcohol solution for 10 minutes was carried out for development of hydrophilicity. The thickness of the thus obtained polymer was 250 nm on average according to confirmation by UHR-FE-SEM. In addition, the thus obtained composite separation membrane was subj acted to a reverse osmosis test under the conditions of 0.5 MPa and 25° C., with the use of, as raw water, a 500 ppm salt solution adjusted to pH 6.5 with hydrochloric acid or sodium hydroxide, thereby obtaining the performance shown in Table 1 as the result of the test. In addition, the thickness of the thus obtained polymer was 250 nm on average according to confirmation by UHR-FE-SEM.

Example 2

[0050]A composite separation membrane was produced in the same way as in Example 1, except that an isopropyl alcohol solution containing 1.8 weight % of an acrylic acid, 0.2 weight % of Methacryl-POSS, and 0.12 weight % of 2,2-dimethoxy-2-phenyl acetophenone was used instead of the solution applied onto the porous supporting membrane in Example 1. The thus obtained composite separation membrane was evaluated in the same way as in Example 1 to obtain the performance shown in Table 1.